New slbo-Gal4 driver lines for the analysis of border cell migration during Drosophila oogenesis.

Border cell (BC) migration during Drosophila oogenesis is an excellent model for the analysis of the migratory and invasive cell behavior. Most studies on BC migration have exploited a slbo-Gal4 driver to regulate gene expression in these cells or to mark them. Here, we report that the slbo-Gal4 transgene present in the line #6458 from the Bloomington Stock Center is inserted within chickadee (chic), a gene encoding the actin-binding protein Profilin, which promotes actin polymerization and is known to be involved in cell migration. The chic6458 mutation caused by the transgene insertion behaves as a null chic allele and is homozygous lethal. To evaluate possible effects of chic6458 on the assessment of BC behavior, we generated new lines bearing the slbo-Gal4 transgene inserted into different second chromosome loci that do not appear to be involved in cell migration. Using these new lines and the slbo-Gal4-chic6458 line, we defined the functional relationships between the twinfilin (twf) and chic in BC migration. Migration of BCs is substantially reduced by mutations in twf, which encodes an actin-binding protein that inhibits actin filament assembly. The defects caused by twf mutations are significantly suppressed when the slbo-Gal4-chic6458, but not the new slbo-Gal4 drivers were used. These findings indicate twf and chic interact and function antagonistically during BC migration in Drosophila oogenesis.